Mobile communication devices, such as mobile phones are now ubiquitous. In addition, most mobile phones include cameras, and in many instances high resolution cameras, which allow users the ability to capture images of documents as well as natural scenes. In addition, electronic documents have rapidly gained acceptance as a convenient replacement for conventional paper documents. To this end, people are increasingly using their mobile phones to capture images of documents. For example, digital images of documents, receipts, menus, flyers, magazines, and other text are frequently captured for dissemination or for use in applications such as optical character recognition (OCR). Yet, using mobile phones to capture document images in this manner commonly results in the introduction of shadows into these images. And, the presence of shadows is undesirable and degrades the quality of the captured document images.
Digital image editing applications are available that provide shadow removal capabilities. For example, after capturing a document image, a user can use any of these applications to, for instance, remove the shadowing within a given document image. Many of these editing applications typically utilize a shadow mask of a document image to remove the shadows from the document image. However, in addition to identifying areas of shadows in a document image, a shadow mask may also include dark regions that inadvertently identify image contents, such as dark surfaces, dark objects, and drawings, in the document image. That is, the shadow mask may identify both regions of shadows and regions of image contents that are present in the document image. As a result, using a conventional shadow mask to remove the shadows from a document image can degrade the quality of image contents in the document image which were inadvertently identified in the shadow mask.
In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be used, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. The aspects of the present disclosure, as generally described herein, and illustrated in the Figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein.